1. Field
Embodiments relate to a flat panel display (FPD) with a built-in touch screen and a method of driving the same. More particularly, embodiments relate to a sensor scan driver capable of supplying stable driving signals to photodiodes for performing the function of a touch screen and a FPD with a built-in touch screen including the same.
2. Description of the Related Art
A touch screen is provided on the top surface of an image display so that a person may select instruction contents displayed on the screen of the image display by a hand or an object and contacts the hand or the object. The touch screen grasps a contact position and the image display receives the content instructed by the contact position as an input signal to be driven in accordance with the input signal.
Since the image display having the touch screen does not need an additional input device, e.g., a keyboard and a mouse, coupled to the image display to be driven, the use of the image display having the touch screen is increasing.
Recently, the touch screen is widely used for the FPD such as a liquid crystal display (LCD) and an organic light emitting display (OLED). The FPD having the touch screen includes a display panel for displaying an image and a touch screen panel provided on the display panel to detect position information through touch input from a user.
When the display panel and the touch screen panel are additionally provided and the touch screen panel is attached onto the display panel, the entire optical characteristic of the FPD may deteriorate, manufacturing cost increases, and the thickness of the FPD increases. Therefore, the touch screen panel and the display panel are integrated with each other to realize the FPD with the built-in touch screen.
For example, photo sensors realized by photodiodes are formed in non-pixel regions between the pixels of the display panel so that a change in optical current generated by a touch event from the user is sensed so that a touch position may be sensed.
In the above-described FPD with the photo sensor type built-in touch screen, the plurality of photodiodes are formed on the display panel and driving signals are sequentially supplied to the photodiodes to sense the optical current.
Therefore, a sensor scan driver for sequentially supplying the driving signals to the photodiodes may be provided in the FPD with the photo sensor type built-in touch screen. The sensor scan driver may include a shift register for sequentially shifting input signals like a common scan driver and a level shifter for shifting the voltage of the signal output from the shift register to a desired level. The level shifter may include a plurality of transistors coupled between a first power source and second power source, and during transitory phases, respective ones of the transistors may be simultaneously turned on such that a path may exist between the first power source and the second power source. When such a level shifter is employed, during a transition period where a level of first and second input signals may rise from a low level to a high level or fall from a high level to a low level, leakage current may be generated and power consumption may increase. As a result of such leakage current, a circuit may erroneously operate and an output signal generated therefrom may be unstable. More particularly, e.g., when a sensor scan driver employs such a common level shifter driving signals may not be stably supplied to photodiodes of the touch screen panel.